This is a really easy quiche recipe that I've been making for years. The best part is the super simple crust made with cracker crumbs and butter. You can subsitute the spinach for pretty much anything, and while I love the salty sharpness of Gruyère which also melts well, you can use Cheddar or any grated cheese you'd like.
Preheat the over to 350 degrees. Put the entire sleeve of crackers into a blender or food processor with the melted butter and blend until the crackers are crumbs. Press into a pie pan and put in the oven for 5 minutes until it puffs up a bit and browns.
Meanwhile, heat the olive oil in a frying pan and add the onions. Cook for 5 minutes on medium heat until softened. Add the spinach and sauté until wilted. Remove the pan from heat and set aside.
In a bowl, whisk 4 eggs with the heavy cream and cheese. Stir in the nutmeg and pepper (I usually don't add salt because the cheese is salty but here is a good time to add salt if you wish). Spread the spinach and onions evenly over the crust that has now hopefully hardened. Pour the egg mixture on top.
Bake for 35 minutes. If you have a meat thermometer, stick it in the middle after 30 minutes and if it's at 158 degrees, your quiche is ready. Voilá.